Or search: bust, gnaw, rust, wilt, decay, droop, erode, tumble, corrode, crumple, collapse, dilapidate, disintegrate
2 Syllables: SU
bundle, crumbled, crumpled, frontal, fumbled, funnel, grumble, humble, jumble, jungle, mongrel, mumbled, rumble, stumble, Trumbull, tumble, tunnel, uncle
3 Syllables: USU
autumnal, disgruntled, triumphal

Found 21 words across 2 groupings. Skipped 14 excess words of a similar stem.